It has been known to provide an hour meter for a gas turbine engine. The hour meter simply displays a total number hours of operation of the gas turbine engine. This information is useful in providing information for establishing maintenance and overhaul schedules for each turbine engine model.
Because the hour meter does not display information which considers the duty cycle of the engine (firing temperature, number of starts, output, and the like) the frequency of maintenance and overhaul is often in error. Such error may result in excessive servicing on one hand or inadequate servicing on the other. In cases where excessive servicing is provided the cost of engine operation is increased. In situations where inadequate servicing is provided premature engine wear and failure may occur resulting in unnecessary down time.
The behavior of rotors, nozzles, blades, combustors, and other components of the turbine engine under various temperatures and stresses affect the life of the turbine engine. The alloy material used, for example, in the blades, nozzles, combustors and other components of the gas turbine engine affects the life of the gas turbine engine. This criteria has often been ignored during the establishment of the engine service schedule. Thus, inadequate servicing often results.
Since an hour meter display merely depicts the number of hours of operation of the gas turbine engine and does not consider factors related to the duty cycle, materials, and the like of a particular engine model and engine installation, there is inadequate information for a service technician to make an accurate judgement call related to the service requirements.
The manufacturer of the engine frequently provides a maintenance schedule to the user based on historical data. The schedule advises the user to service the engine at fixed periods of time. These service intervals include a safety factor. The safety factor considers that the engine is operating at a particular duty cycle. This may however not be the case and may result in too frequent service intervals.
Creep, low cycle fatigue, and temperature shock effects on gas turbine engines may lead to catastrophic turbine engine failure. These effects are not discernible through a reduction in the performance of the engine. However, such effects are predictable based on equations developed by analytical and empirical testing. Attempts have been made to determine engine life using techniques such as disclosed in U.S. Pat. No. 3,584,507 to Rudolph Hohenberg dated Jun. 15, 1971. This patent teaches sensing temperature (T7) and speed and determining creep, low cycle, and temperature shock fatigue based on these parameters and certain constants assigned to different engine models. This technique, although an improvement over the hour meter, is not complete as it does not consider all of the significant parameters, such as, a completed engine starting.
The present invention is directed to overcoming one or more of the problems as set forth above.